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Selective Palladium-Catalyzed Dehydrogenation of Limonene to Dimethylstyrene

  1. Patricia Horrillo-Martínez Dr.1,2,
  2. Marie-Alice Virolleaud Dr.1,3,
  3. Christoph Jaekel Dr.1,4

Article first published online: 5 JAN 2010

DOI: 10.1002/cctc.200900200

Issue

ChemCatChem

ChemCatChem

Volume 2, Issue 2, pages 175–181, February 8, 2010

Additional Information

How to Cite

Horrillo-Martínez, P., Virolleaud, M.-A. and Jaekel, C. (2010), Selective Palladium-Catalyzed Dehydrogenation of Limonene to Dimethylstyrene. ChemCatChem, 2: 175–181. doi: 10.1002/cctc.200900200

Author Information

  1. 1

    Catalysis Research Laboratory (CaRLa), Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 584,D-69120 Heidelberg (Germany), Fax: (+49) 621-606656351

  2. 2

    Present address: Department of Chemistry, University of British Columbia 6174 University Blvd., Vancouver, BC, V6T 1Z3 (Canada)

  3. 3

    Present address: UPCAM iSm2 Service 531, Campus Scientifique de St Jérôme 13397 Marseille cedex 20 (France)

  4. 4

    GCB/C-M313, BASF SE,D-67056 Ludwigshafen (Germany)

Publication History

  1. Issue published online: 1 FEB 2010
  2. Article first published online: 5 JAN 2010
  3. Manuscript Revised: 6 NOV 2009
  4. Manuscript Received: 21 JUL 2009

Funded by

  • Heidelberg University
  • state of Baden-Württemberg,
  • BASF

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Keywords:

  • aromaticity;
  • C[BOND]H activation;
  • heterogeneous catalysis;
  • homogeneous catalysis;
  • palladium

Abstract

Conditions for the selective dehydrogenation of (+)-limonene 1 to the polymer building block dimethylstyrene 2 are described. The reaction occurs smoothly in the presence of Pd(OTFA)2 as catalyst and CuCl2 as oxidant. High selectivity for retaining the exocyclic double bond during aromatization is achieved (>14:1). Initially, variable-temperature NMR experiments, under stoichiometric conditions, showed a stepwise formation of a π-allyl intermediate and subsequent reaction to give a mixture of products. However, kinetic experiments showed a sigmoidal curve, pointing to the heterogeneous nature of the catalytically active species. A number of experiments were undertaken to differentiate between homogeneous, molecularly defined catalysis and heterogeneous, nanocluster-based catalysis. Based on the results, it is proposed that the true catalytic system is heterogeneous in nature.

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